Archive for January 14, 2019

Bernard Schutz wins the 2019 Eddington Medal

Posted in Cardiff, The Universe and Stuff with tags , , , on January 14, 2019 by telescoper

I wasn’t able to get to the Ordinary Meeting of the Royal Astronomical Society on Friday 11th January as I was otherwise engaged. In case you didn’t know, these meetings happen on the second Friday of every month and consist of short talks, longer set-piece prize lectures and Society business. The January meeting is when the annual awards are announced, so I missed the 2019 crop of medals and other prizes. When I got to the Athenaeum for dinner I was delighted to be informed that one of these – the prestigious Eddington Medal – had been awarded to my erstwhile Cardiff colleague Bernard Schutz (with whom I worked in the Data Innovation Research Institute and the School of Physics & Astronomy).

Here is a short video of the man himself talking about the work that led to this award:

The citation for Bernard’s award focuses on his invention of a method of measuring the Hubble constant using coalescing binary neutron stars. The idea was first published in September 1986 in a Letter to Nature. Here is the first paragraph:

I report here how gravitational wave observations can be used to determine the Hubble constant, H 0. The nearly monochromatic gravitational waves emitted by the decaying orbit of an ultra–compact, two–neutron–star binary system just before the stars coalesce are very likely to be detected by the kilometre–sized interferometric gravitational wave antennas now being designed1–4. The signal is easily identified and contains enough information to determine the absolute distance to the binary, independently of any assumptions about the masses of the stars. Ten events out to 100 Mpc may suffice to measure the Hubble constant to 3% accuracy.

In this paper, Bernard points out that a binary coalescence — such as the merger of two neutron stars — is a self calibrating `standard candle’, which means that it is possible to infer directly the distance without using the cosmic distance ladder. The key insight is that the rate at which the binary’s frequency changes is directly related to the amplitude of the gravitational waves it produces, i.e. how `loud’ the GW signal is. Just as the observed brightness of a star depends on both its intrinsic luminosity and how far away it is, the strength of the gravitational waves received at LIGO depends on both the intrinsic loudness of the source and how far away it is. By observing the waves with detectors like LIGO and Virgo, we can determine both the intrinsic loudness of the gravitational waves as well as their loudness at the Earth. This allows us to directly determine distance to the source.

It may have taken 31 years to get a measurement, but hopefully it won’t be long before there are enough detections to provide greater precision – and hopefully accuracy! – than the current methods can manage!

Congratulations to Bernard on his thoroughly well-deserved Eddington Medal!

 

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